The long term objectives of this application are to define, in molecular terms, the initial biochemical and physiological responses of the neutrophil to chemotactic agents. In this work, particular stress is laid on delineating the nature and role of the cellular enzymes activated in these responses. The initial aim is to refine the model of the formylpeptide receptor of the rabbit neutrophil previously described and extend it from the portion accommodating tripeptides to the area accommodating tetrapeptides. Efforts to obtain highly active specific antagonists of the formylpeptide receptor will continue. The study of the interrelationships of two series of boc methyl esters with fMet-Leu-Phe and other chemotactic factors on granule enzyme secretion, chemotaxis and other neutrophil functions will be continued. Particular attention will be paid to obtaining evidence testing the working hypothesis that the inhibition of the secretory activity of the boc methyl esters by fMet-Leu-Phe is due to the evocation of two inhibitory signals, one from the reaction of fMet-Leu-Phe with the neutrophil, the other from the action of the boc methyl ester. Attempts will be made to establish that DFP inhibits the activation by chemotactic factor of the Na+, K+-ATPase by interfering with the activation of a serine esterase. For this purpose, use will be made of the uptake of H3[DFP]. In addition, the mechanisms by which chemotactic factors activate the phospholipase A2 of isolated plasma membranes of neutrophils will be further studied. To this end, the effects of deoxycholate and various combinations of chemotactic factors acting at separate receptors will be investigated. In addition, attempts will be made to see whether chemotactic factors can increase the acyl-transferase activity of isolated plasma membranes and relate the increased activity and the activation of phospholipase A2-A2 to change in the endogenous phospholipids of the same membranes.